Laboratories for Metrology
The constant precise control on Temperature is a fundamental key element for Dimensional Metrology according to the International Standard ISO 1 that fixes the reference Temperature at 20°C for geometrical specifications; the requirements are generally different depending on the applications fields, on the measurements accuracy provided by the testing equipments (CMM) and on mechanical parts which have to be analyzed.
Even if the requirements specify that it is not compulsory that all calibrations and tests for the acceptance of mechanical and electro-mechanical parts should be carried out at 20°C it mentions only that a measurement done at a different temperature may lead to apply an offset value on final results contributing to a considerable increase of measure uncertainty and consequently to a lowering of the quality, of the traceability and of the comparability of tests.
Calibrations and measurements with CMM as large bridge-type machines, bridge-type measuring machines and servo-driven gantry style machine, etc. are performed in controlled spaces with different air volumes but always at a stable Temperature control as close as possible to 20°C and with a reasonably low percentage of R.H.(%) to reduce at minimum the temperature correction functions outputting more reliable and realistic measurements.
Acceptable limits about temperature gradients are around ± 0,5°C, which has to be set in order to define clearly how much temperature could deviate from 20°C during the test activities without penalizing too much the quality of measurements. Therefore it is definitely necessary that the air conditioning system maintains the temperature and possibly the R.H. (%) under control with a PID adjustment in order to keep its gradients very low within the laboratory apparatus.
The instruments required to measure the barometric air pressure, air temperature and relative humidity
The laboratory maintains documented uncertainty measurements results
Using air conditioners and de-humidifiers.
The barometric pressure in the laboratory should be recorded.
The value of local acceleration due to gravity (g) local should be measured /known to the best possible measurement uncertainty.
Branca Idealair offers three solutions for Metrology laboratories:
SOLUTION 1 : The Climatic Element - Branca Idealair
High accuracy measurements with the precision air conditioning handled from the "Climatic Element Branca Idealair" with a proper thermal insulation of laboratory followed by specialized technicians from S.T.A. Branca Idealair able to guarantee the thermo-hygrometric parameters below:
Select your "Laboratory cubic meters air volume (m3)" to get more information:
SOLUTION 2: CABINET
Solution 2 is provided by an insulated chamber with Climatic unit Type "CABINET" that ensures the following reference ambient parameters:
SOLUTION 3 : MEASURE BOX
Available various air volumes specified chosen by the customer the "Measure box" is the ideal solution to get an extremely satisfactory precision air conditioning of parts (for example commonly used for Johnson gauge blocks) inside a small air volume preliminary chosen by the customer and guaranteeing the tolerances here below:
Prof. Guglielmo M. Tino (Dipartimeto di Fisica e Astronomia and LENS Laboratory)
Università degli Studi di Firenze
Istituto Nazionale di Fisica Nucleare, Sezione di Firenze
POLO scientifico - Via Sansone 1 I-50019 Sesto Fiorentino (Firenze) ITALY
Tel.: +39 055 457-2034 (Office) - 2214 (Lab), - 2462 (Lab)
Fax.: +39 055 457-2121
"... In several occasions I had the opportunity to advice other colleagues about your excellent realization of the precision air conditioning system of our MAGIA laboratory; that was an essential element for the success of the MAGIA experiment whose goal was the accurate measurement of the gravitational constant G which is a fundamental physical constant of metrological interest. ..."
Dott. Vincenzo Greco (CNR Istituto nazionale di ottica)
Largo Enrico Fermi, 6 50125 Firenze (Italy)
Tel.: +39 055 2308271
Fax.: +39 055 2337755
"... As anticipated by phone call we perform temperature measures inside our conditioned room for a period of 3 hours with time sampling of 5 minutes. The data anlyses shows that in 1 hour the flunctuation of temperature values in correspondece to the average value is +/- 0,1 °C (measure uncertainty 2 sigma that represents for a normal distribution corresponds to a level of reliability of 95%) ... "